BRUSSELS (AP) — The European Union's anti-trust watchdog said Tuesday that it has launched a probe into German chemical maker Bayer's planned acquisition of U.S. seed and weed-killer company Monsanto.

The European Commission, which polices competition in Europe, said it has concerns that the merger may reduce competition in areas like pesticides and seeds.

"We need to ensure effective competition so that farmers can have access to innovative products, better quality and also purchase products at competitive prices," Competition Commissioner Margrethe Vestager said.

Monsanto in September last year accepted an offer from Bayer to pay $57 billion to its shareholders and assume $9 billion in debt. Were it to go ahead, the buyout would create the world's largest integrated pesticides and seeds company.

The Commission says it will also look into whether the move would hinder the access of competitors to distributors and farmers.

Bayer said in a statement that it "had expected further review of the proposed acquisition of Monsanto due to the size and scope of the transaction."

"Bayer believes that the proposed combination will be highly beneficial for farmers and consumers," it said, adding that it "looks forward to continuing to work constructively with the Commission with a view to obtaining the Commission's approval of the transaction by the end of this year."